1. Field of the Invention
The present invention relates to a civil airplane fitted with bypass turbojet engines having nacelles that are partially embedded in the fuselage of the airplane.
2. Description of the Related Art
Present civil airplanes are propelled by turbojets mounted under the wings or in a rear position on the fuselage, and they are attached thereto by means of pylons.
In the context of reducing fuel consumption, engine manufacturers are turning towards partially embedding engines inside the fuselage, thus making it possible to eliminate the pylons and their fairings and consequently reducing the weight of the propulsion assembly. Furthermore, partially integrating the engines in the fuselage enables the diameter of the engines to be increased, thus making it possible to envisage using engines having a very large bypass ratio. Finally, reducing the area of the nacelle that is in contact with air flowing around the airplane serves to reduce drag.
In flight, a boundary layer at substantially zero speed is formed around the fuselage of the airplane and generates aerodynamic drag. It has long been thought that engines ought not to ingest the boundary layer since that could give rise to major distortion in the fan and to shaft vibration, so airplanes have been fitted with boundary layer “traps” that are situated upstream from the air intakes of engines that are partially embedded. Nevertheless, more recent studies have shown that absorbing a portion of the boundary layer in the engines makes it possible significantly to reduce the aerodynamic drag of the airplane and to reduce the speed of the air penetrating into the engines, and thus to increase the efficiency thereof.